Abstract LB154: <i>Peptostreptococcus anaerobius</i> induces colorectal cancer stemness and chemoresistance via its surface protein NIpC/P60 interacting with Annexin A2 to activate YAP/Hippo signaling pathway

Abstract Chemoresistance is a common challenge in colorectal cancer (CRC) and contributes significantly to treatment failure and relapse. Here, we investigate the role of the CRC intratumoral pathogen Peptostreptococcus anaerobius in promoting colorectal cancer stem cell (CSC) stemness and chemoresistance, elucidating its molecular mechanisms. We found that intratumoral P. anaerobius is positively correlated with stemness-related genes, such as CD133 and LGR5, in CRC patients (n=73). Gavage with P. anaerobius enhanced CRC formation and increased the populations of Cd133+ and Lgr5+ cells within CRC tissues from ApcMin/+ and AOM/DSS models, indicating that P. anaerobius promotes CSC characteristics in CRC. Furthermore, co-culture with P. anaerobius significantly increased the self-renewal capacity and sphere-forming ability of human colorectal CSCs, alongside elevated expression levels of CD133 and LGR5. Notably, P. anaerobius also conferred resistance to oxaliplatin and 5-fluorouracil treatment in both human CSCs in vitro and in AOM/DSS-induced CRC models. Mechanistically, we discovered that the outer membrane protein NlpC/P60 from P. anaerobius interacts with the Annexin A2 receptor on colorectal CSCs. Co-immunoprecipitation, SPR assays, and crosslinking MS revealed that NlpC/P60 competed with Yes-associated protein 1 (YAP) for binding to Annexin A2 (ANXA2). This interaction disrupted the intracellular binding between ANXA2 and YAP, leading to the release of YAP from the cell membrane, promoting YAP translocation into nucleus to activate Hippo signaling pathway. Importantly, neutralizing antibodies against ANXA2 blocked the interaction between P. anaerobius and colorectal CSCs, thereby abrogating the effects of P. anaerobius on stemness and chemoresistance. Consistent with these pre-clinical findings, higher levels of P. anaerobius were observed in chemotherapy non-responders compared to responders among CRC patients. In summary, P. anaerobius drives CRC stemness and chemoresistance through the NlpC/P60-Annexin A2 interaction, leading to YAP1-mediated activation of the Hippo signaling pathway. Targeting this interaction may offer a promising strategy to overcome P. anaerobius-mediated chemoresistance in CRC. Citation Format: Liu Yali, Chi Chun Wong, Yating Zhang, Kai Yuan, Chuanfa Liu, Weixin Liu, Mingxu Xie, Jun Yu. Peptostreptococcus anaerobius induces colorectal cancer stemness and chemoresistance via its surface protein NIpC/P60 interacting with Annexin A2 to activate YAP/Hippo signaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB154.